1. Technical Field
This invention proposes an ignition device for a sintering machine, and more particularly an ignition device for a moving grate type sintering machine which employs a burner capable of forming a strip of flame extending continuously over the width of the strand to enable easy control of igniting the raw mix in accordance with operational conditions, and also enable large savings in fuel.
2. Description of the Prior Art
In general, an ignition device for a moving grate type sintering machine employs burners which are positioned over the surface of the raw mix placed on pallets, and which are adapted to burn a fuel such as heavy oil, coke oven gas, or mixed gas consisting of coke oven gas and blast furnace gas, whereby the coke in the raw mix is burnt by the combustion flames of the fuel.
FIG. 1 schematically illustrates a sintering machine in which the ignition device is installed. Referring to the drawing, reference numeral 1 denotes pallets, 2 wind boxes, 3 an ignition device consisting mainly of an ignition furnace 3a and burners 3b, 4 a hearth layer hopper, and 5 a raw mix hopper.
FIG. 2 illustrates a typical, conventional ignition device for a sintering machine which consists of a burner assembly 3b provided with a plurality of burner arrays arranged in the direction of the pallets movement, each of the burner arrays being composed of a number of burners.
In such a conventional ignition device, uneven sintering occurs in the sinter products, and the fuel consumption becomes higher.
FIG. 3 shows the ignition intensity obtained over the width of the strand, when a conventional ignition device is used. As is clear from the figure, the ignition intensity varies in very different values according to the positions immediately under the burners or else. This causes uneven sintering of the sinter ore. In such a case, it was usually necessary to adjust the combustion rate of the burner assembly 3b on the basis of the weakest portion of the transversal ignition intensity so as to prevent the sintered ore from being unevenly sintered. This results in an increase of the energy consumption. Moreover, since each burner has different thermal characteristics, it is very difficult to obtain a uniform ignition intensity over the width of the strand.
Such a conventional ignition furnace 3a has such a vertical dimension as high as 1500 mm on average, so that the is a long distance between the burner tips and the surface of the raw mix. This tends to increase energy losses.
An ignition device provided with a single mixing combustion chamber which has a slit-shaped combustion gas discharge port has been proposed in Japanese Patent Laid-open No. 37685/1982. In this ignition device, not a flame but a kind of high-temperature waste gas is blown out of the slit-shaped discharge port. Accordingly, the ignition device has the following disadvantages.
Since the mixing combustion chamber becomes red-heated, the slit-shaped burner tip forming the combustion gas discharge port is liable to deform. Consequently, the burner tip has to be made of special materials, and the structure thereof is inevitably complicated.
It is difficult to burn a fuel completely in this mixing chamber, and energy losses cannot be prevented because of the large capacity of the ignition furnace. Moreover, an elaborately-constructed, sufficiently-supported furnace body is necessary, so that the cost is higher.